Interaction of Atoms with Nearly Resonant Fields: Self-Induced Transparency

Abstract

The discussion we have presented so far has supposed throughout that the primary quantity of interest, the electric dipole moment per unit volume P can be expanded in powers of the electric field E. The justification for this procedure is the notion that the largest applied fields encountered in practice are very small compared to those encountered by an electron within an atom or a molecule. It follows that the electronic arrangement in the atom or molecule is perturbed only very slightly from that arrangement found in zero applied external field. In the concluding remarks of Chap. 3, we referred to this as the regime of weak nonlinearity. We now appreciate, however, that even though the nonlinearities are weak in the sense just described, their influence can be substantial, as illustrated by our model discussions of second harmonic generation, and the stimulated Raman effect. A bucket full of water may have only a small leak, but if one waits long enough, the bucket will be quite empty.